Field of the Invention
The present invention relates to a picture-taking apparatus having the capability of detecting a point viewed by an eye of a user.
It is known in the art that the point viewed by a user is detected so that the object corresponding to the viewed-point is brought in focus (refer to, for example, Japanese Patent Laid-Open Nos. 1-241511 and 2-32312). The inventor of this invention has also proposed a selection-by-viewing technique in which marks representing various functions such as zooming, fading, etc., are displayed on a viewfinder screen of a video camera so that a user can select one of these by viewing a desired mark (Japanese Patent Application No. 4-202).
However, there are some problems in a technique in which the focus area moves to follow the viewed-point. That is, a user must always view an object to be focused. If the user makes a quick scan over the entire area of a viewing screen with his/her eye to know the features of a scene, the focus area moves quickly to follow the movement of the viewed-point, which results in an unsightly image. Even if the user tries to view an object as fixedly as he/she can, the viewed-point always moves slightly because human eyes have small movements called flicks that cannot be controlled. Therefore, the AF (autofocus) area in the viewfinder flickers following the movement of the viewed-point, which may be offensive to the eye of the user.
Furthermore, another problem occurs if the mechanism for automatically focusing an image at a moving point viewed by a user is combined with the selection-by-viewing mechanism proposed by the inventor of the present invention in Japanese Patent Application No. 4-202. That is, when the AF area is in the middle of movement to follow the point viewed by a user, if the user views a selection-by-viewing mark displayed in a peripheral area of the viewfinder to use the selection-by-viewing capability, then the AF area also moves following the movement of the viewed-point and thus an object different from the desired one is unintentionally brought in focus.
Furthermore, in tracking AF techniques used in conventional video cameras in which the focus area moves to follow a moving subject, if the subject to be focused is in an end area of the viewing screen, a user has to move the subject to the middle of the viewing screen because the focus area initially is located at the middle of the viewing screen. Moreover, if an object that is tracked by the AF mechanism crosses another object located at a distance similar to that of the tracked object, there is a possibility that the correct tracking is lost.